The present invention concerns gas burners of the kind that are used, for example, in cooking stoves. In the following specification the invention will be described with reference to gas burners for cooking stoves, it being understood that it is not confined thereto and that the gas burners according to the invention may also be installed in other appliances that use gas burners, such as, for example, heating stoves for various domestic and industrial applications.
More specifically the invention is concerned with the design of the head section of a gas burner, i.e. the section at which a flame is produced by combustion of a gas/air mixture. In the following specification and claims the head section of a gas burner will at times be referred to for short as "head".
Conventional gas burner heads comprise a single piece upper circular plate resting on a dish-shaped base in such a way that a gas chamber is formed between the plate and base, means being provided for supplying a pressurized gas/air mixture to the gas chamber. The rim of the upper plate comprises in even distribution a plurality of radially extending orifices or nozzles (hereinafter "nozzles") which serve for the ejection of a gas/air mixture for combustion. In this manner a circumferential flame is formed around the head, consisting of a plurality of discrete, conically shaped flames each associated with one of the nozzles.
This conventional arrangement has a number of drawbacks. Thus, upon ejection of the pressurized gas/air mixture through the nozzles, the gas jet emerging from each nozzle produces around it a zone of reduced pressure whereby ambient air is sucked into the mixture with the consequence that the gas/air mixture fed to the flame for combustion is richer in air than the mixture delivered to the gas chamber. It may accordingly happen that the burning gas/air mixture comprises an excessively high proportion of air which may result in inefficient combustion and produce flames of relatively low temperatures.
For proper functioning, the gas/air mixture delivered for combustion must be prepared in the gas chamber by heat emanating from the burner's top. In known gas burners in which the radially extending nozzles are at a level somewhat below the top, such preheating is hampered by a stagnant pocket of hot gas/air mixture accumulating between the nozzles and the top and functioning as an insulator. In consequence direct contact between the burner's top acting as heat source and the through-flowing gas/air mixture is obstructed and preheating thereof is ineffective. Such ineffective preheating is a further contributing factor to inefficient combustion in prior art gas burners.
Yet another drawback of the conventional head design of gas burners is insufficient heat transfer from the flame to the vessel that is being heated. This is so because the circumferential flame produced by conventional gas burners engulfs the vessel and in consequence there is no or only insufficient direct contact between the flame and the bottom of the vessel and moreover a significant part of the heat from the engulfing flame is dissipated and lost to the ambient atmosphere.
Yet another disadvantage of the conventional head design is the fact that if the contents of the vessel that is being heated spills over, the spilt over matter comes in direct contact with the nozzles and clogs them. The cleaning of clogged nozzles is a tedious operation requiring a series of manipulations which is yet another disadvantage.
Still a further disadvantage is due to the very fact that the flame in conventional burner heads consists of a plurality of discrete flames each associated with one nozzle, since when one such flame becomes extinct, for example in consequence of an air current, it is not always re-kindled. It may thus happen that in consequence of an air current part of the individual flames are extinguished with noncombusted gas continuing to stream out of the nozzles, which obviously is an undesired phenomenon.
It is the object of the present invention to provide a new kind of gas burner head free of the disadvantages of the prior art.